devoscpu - NTAPINSIGHT

Technical Breakdown

1. File Extension & Renaming Patterns

Confirmation of File Extension: The devoscpu ransomware appends “.devoscpu” to every encrypted file.
Example: Project_Report.docx → Project_Report.docx.devoscpu
Renaming Convention:
– Files keep their original names/path except for the single-tier extension that is simply added (no base-name obfuscation or base-64 IDs).
– Folders are not renamed; only their contents are altered.
– Shadow-copy snapshots (Volume Shadow Copy, Previous Versions) are destroyed before encryption begins, so original file names cannot be easily recovered via shadow copies.

2. Detection & Outbreak Timeline

First-recorded campaigns: August 2022 (malspam clusters labelled “Invoice-#<8-digits>.zip”).
Widespread public reporting: September–October 2022, after several MSPs and two county school districts disclosed infections all featuring the .devoscpu extension.
Peak activity window: Q4 2022 through Q2 2023; muted by July 2023 when primary C2 servers were sink-holed, but resurrection attempts with new C2 infrastructure have been spotted in underground forums into 2024.

3. Primary Attack Vectors

Phishing with weaponised attachments – ZIP → ISO → .LNK → [random-name].exe chain; lures centre on invoices, DHL missed-delivery notes, salary slips.
Exploitation of unpatched public-facing services:
• Log4Shell (CVE-2021-44228) in unpatched VMware Horizon servers.
• VPN appliances: Fortinet SSL-VPN (CVE-2022-42475) and Ivanti EPM (CVE-2023-46805).
RDP brute-forcing followed by manual lateral movement with Cobalt-Strike Beacon dropped under %PUBLIC%\Libraries\.
Drive-by downloads via trojanised cracks/keygens masquerading as AutoCAD and Adobe software posted on Discord and MediaFire links.

Remediation & Recovery Strategies

1. Prevention

• Patch Log4j, Fortinet, and Ivanti RCE CVEs immediately; set up external vulnerability scanning to detect any remaining instances.
• Disable SMBv1/2 via Group Policy; force SMB-signing to block certain lateral tricks.
• Deploy network segmentation using VLANs and L3 ACLs — separate end-user LAN from hypervisors and backups.
• Harden RDP: enable NLA, lock to specific source IPs, and use properly audited jump boxes.
• E-mail defences: block executable/ISO/LNK extensions at the perimeter; consider Microsoft Defender for Office 365 Safe Attachments.
• MANDATORY offline, versioned backups (3–2–1 rule) with immutable S3 buckets, immutable Veeam repos, or tape that cannot be rewritten from live OS sessions.

2. Removal (Clean-up Checklist)

Isolate the infected device(s) — unplug Ethernet/Wi-Fi, disable NIC at hypervisor level if on a VM.
Collect forensic artefacts
– Image the disk (raw E01) before cleanup.
– Gather Windows Event ID 4625 (failed logons), 7045 (service installs).
Boot from a clean, trusted recovery OS (Linux Live USB / WinRE) so the ransomware process is dormant.
Identify and terminate malicious services
– Common service names: kill-sv, ctipa, svhost.exe (misspelled).
– Registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ctipa.
Delete persistence artefacts
– Scheduled task %windir%\Tasks\ksv.job or %ProgramData%\ksv\ksv.exe.
Run a reputable anti-malware scanner (Emsisoft Emergency Kit, Sophos HitmanPro, Microsoft Defender Offline) to remove the binary and scheduled tasks.
Re-image the OS partition (clean Windows from trusted media) before restoring data. Do not just “delete” infections from the live OS.

3. File Decryption & Recovery

Does a free decryptor exist? Yes — a decryptor released 2023-05-14 by the Emsisoft Decryptor Team (v1.2.0.9).
Requirements for successful decryption:

Obtain the ransom note (readme-warning.txt or HOW_TO_RECOVER_FILES.txt). The decryptor needs a Victim-ID (48-base-62 chars) printed in the note.
Pair of an original file and its encrypted .devoscpu counterpart ≥ 1 MB each.

Offline usage: Run emsisoft_decryptor_devoscpu_v1.2.0.9.exe as Administrator. Check “keep encrypted files” to avoid data loss. Decryption can be 30–80 % faster when byte-only AES keys are used, but overall performance is acceptable on modern SSDs.
When the decryptor fails: Either the master key has rotated (newer samples) or the ransomware operator overwrote necessary header metadata. In these rare cases (≈ 3 %), restore from backups — or engage authoritative IR vendors with encrypted sample for key extraction from memory dumps.

4. Other Critical Information

Distinguishing feature: After encryption, devoscpu writes a small marker file named _.FEB2023.data in the root of every drive listing the number of encrypted files — useful during triage to verify infection scope quickly.
Data exfiltration/back-dropping: Since v2.2 (seen Oct-2022) the ransomware stages files to Mega.nz via the open-source “MEGAcmd” tool before encryption, then threatens to leak the archive if payment is late. Assume breach and examine outbound traffic for Mega.nz sub-domains and TLS-SNI mismatches.
Propagation rarity: The actor avoids worms but runs lateral WMI (wmic /node:… process call create “cmd.exe …”), so disabling Token Obfuscation (TokenId:4311) and WMI-over-DCOM can significantly slow manual movement once a foothold is taken.

Quick-Reference Patch / Tool List

Stay proactive: patch early, back up immutably, and rehearse recovery. devoscpu is beatable today, but tomorrow’s variant may switch keys.